The present invention relates to fasteners employed to fasten a covering material to an underlying substrate. More particularly, the invention relates to a plastic/metal composite batten bar with a fastener for fastening a membrane, such as a roof membrane or roofing insulation, to a roof deck.
Reported Development
Fasteners are conventionally employed in the building industry for fastening or clamping a flexible membrane, such as an insulation membrane to a substrate, such as a roof deck. The fasteners typically comprise a large head portion and a shank portion. In use, the shank portion is driven through the membrane into the underlying substrate to anchor the fastener thereinto, while the head portion holds the membrane against the substrate and prevent removal thereof by wind lift. The undersurface of the head portion is typically provided with gripping means so that the membrane is prevented from moving or sliding under the fastener. Conventional fasteners are illustrated by the following references.
U.S. Pat. No. 4,787,188 discloses a stress plate for securing a roof membrane to a roof deck. The stress plate is circular having a top surface and a bottom surface with a central circular opening for receiving a screw for fastening the stress plate over a roof membrane and to the roof deck. The stress plate is equipped with four gripping prongs of triangular shape which are circumferentially spaced from each other by 90xc2x0.
In use a first membrane is applied to a roof deck surface, then the membrane is secured to the roof deck surface with the stress plate and the screw. A top sheet or membrane is lapped over the first membrane to cover the stress plate and welded to the first membrane. The four gripping prongs in the stress plate grip the first sheet and hold the same on top of the roof deck without tearing.
U.S. Pat. No. 5,049,018 discloses a fastener for gripping a substrate material. The fastener is of a unitary piece comprising a head portion, a shaft portion, and a hook portion at the end of the shaft portion, wherein the hook portion has an outwardly and upwardly extending resilient end portion. The end portion has an end surface which provides gripping contact with a wall of a hole in a substrate into which the fastener is inserted.
U.S. Pat. No. 5,163,798 relates to a fastener assembly which is employed to secure plies or membranes of roofing, felt and paper to prevent the materials from being blown off the base roofing material before the base material is sufficiently hardened.
The assembly comprises a fastener and a retainer plate. The assembly includes a fastener plate which defines a substantially rectangular opening. The fastener includes a head and a pair of legs which are integrally hingably connected to the head. The legs have a contoured distal portion and an angular side configuration so that at least one of the legs is forced apart as the fastener is driven into the base material.
We have observed that under windy conditions the prior art fasteners need improvement in securely holding a flexible membrane on a substrate without the gripping means penetrating the flexible membrane, and without tearing the flexible membrane.
Asphalt roof membranes to prevent moisture from entering into an underlying roof deck are being replaced by thermoplastic sheet materials which offer a superior, longer-lasting roof at a lower cost. In the process of installing thermoplastic sheet materials over a roof deck, the typical steps are as follows. A first sheet is laid adjacent to the lower edge of the roof and running parallel thereto. Fastening means, such as batten bar or a line of stress plates are positioned near the upper edge of the first sheet. Fasteners are inserted through the batten bar or stress plates and into the roof deck to securely hold the first sheet to the roof deck. Then a second sheet is laid over the roof deck in a marginally overlapping relationship with the first sheet. The second sheet also overlaps the batten bar or the line of stress plates. The overlapping edge area of the second sheet overlaps the area of the first sheet on both sides of the batten bar or line of stress plates. A weld is then applied between the first sheet and the second sheet resulting in the fusion of the two sheets on both sides of the batten bar or the line of stress plates. The weld is applied by the use of a welding machine or tool which softens the thermoplastic sheets and, after cooling, solidifies and forms a continuous sheet. The steps are repeated until the roof deck is completely covered by the thermoplastic sheets.
It has been observed that stress plates having a high profile create bumps in the weld area. It has also been observed that stress plates made of metals and a plastic that is not heat weldable do not adhere to the second or overlapping thermoplastic sheet thereby creating bubbles in the weld. Accordingly, it is an object of the present invention to provide a batten bar which substantially remains in the plane of the thermoplastic sheets and which is coated with a thermoplastic material so that the second or overlapping sheet is also welded to the batten bar.
This aspect will be addressed as the description of the invention proceeds, followed by a method of using the batten bar for fusing thermoplastic sheets over a roof deck.
In a device aspect, the present invention comprises a metal batten bar having a top surface and a bottom surface coated with a thermoplastic material on the top surface thereof. The composition of the batten bar consists of a metal, such as steel, galvalum or galvanized metals preferably having a thickness of about 0.25 to 3 mm, and a thermoplastic layer preferably having a thickness of about 0.25 mm to 2 mm. Softer metals such as copper and aluminum may also be used, however, the thickness of the batten bar should be larger to provide sufficient integrity to the batten bar. The thermoplastic material coating the batten bar may be polyvinyl chloride, thermoplastic olefins, chlorinated polyethylene, chlorosulfonated polyethylene, nylon, ethylene propylene diene rubber or any other heat weldable thermoplastic composition. The batten bar is provided with openings at 6xe2x80x3 or more intervals to allow fasteners therethrough, such as screws for securing the same to thermoplastic sheets and the underlying roof deck insulation and/or cover board. The fastener is preferably a screw member having threads thereon. The thermoplastic material must be compatible with the thermoplastic roofing membrane i.e., it must fuse thereto upon the application of heat and pressure.
In the method aspect, the present invention comprises the steps of:
a) laying a first thermoplastic sheet or membrane on a portion of the roof deck;
b) laying a batten bar near the edge of the thermoplastic sheet or membrane parallel to the edge;
c) securing the first thermoplastic sheet or membrane on the roof deck by inserting fasteners through the batten bar, the first thermoplastic sheet or membrane and into the roof deck insulation and/or cover board;
d) laying a second thermoplastic sheet or membrane on the roof deck in an overlapping relationship to the batten bar and the first thermoplastic sheet or membrane; and
e) applying heat and pressure to the overlapped portion of the thermoplastic sheets or membranes on both sides of the batten bar and over the batten bar thereby causing a fusion of the thermoplastic sheets or membranes and to the batten bar.
The heat weld may be accomplished by a welding machine known in the art, such as described in U.S. Pat. Nos. 4,259,142, 4,289,552, 4,440,588, 4,533,423, 4,861,412, 4,894,112, 5,110,398, and 5,935,357. However, we prefer to use a welding machine which is disclosed in co-pending application Ser. No. 09/190,373 and comprises a pressure roller and a heating element for a welding apparatus for producing a weld simultaneously on each side of a line of fasteners and over the fasteners. The pressure roller is integral with an axle designed to be connected to a driving means at one end thereof; at the other end of the axle the pressure roller comprises a distal end, a proximal end and a center portion which defines a groove between the proximal and distal ends. The groove of the pressure roller carries an elastomeric cushion designed to smoothly ride over a line of fastening means.
The pressure roller is used in combination with a heating element containing a blower which forces heated air through a nozzle. The nozzle having an outlet therein preferably comprises three portions: two large opening portions and a restricted opening portion therebetween. In use, the large opening portions allow delivery of the major portion of the hot air produced by the heating element while the restricted opening still allows delivery of sufficient amounts of the heated air to soften the overlapping portions of the thermoplastic sheet over and under the fastening means.